Production of olefins from gaseous or vaporous saturated hydrocarbons



Sept. 26, 1939. H. KLEIN ET AL 2,174,288

PRODUCTION OF OLEFINS FROM GASEOUS 0R VAPOROUS SATURATED HYDROCARBONSFiled May 29, 1936 reacton tube )gydrocarbon hydroca nbon reachon tubeFig/Z -mixirz g 3021a capidlaay tube oxygen --r'ea0150'011 one HansKdezln Ferdinand Haubach Widhelm Hof'editz l INVENTORS THEIR ATTORNEYSPatented Sept. 26, 1939 PRODUCTION OF OLEFINS FROM GASEOUS OR \S'APOROUSSATURATED HYDROOAR- BON Hans Klein, Mannheim, Ferdinand Hanbach,'Lndwigshafen on the Rhine, and Wilhelm Hofeditz, Mannheim, Germany,assignors to I. G. Farbenindustric Aktiengesellschaft,Frankfort-on-the-Main, Germany Application May 29,

1938, Serial No. 82,448

In Germany June '1, 1935 9 Claims.

The present invention relates to improvements in the manufacture andproduction of olefins from gaseous or vaporous saturated hydrocarbons.

It has already been proposed to convert gaseous or vaporous (hereinaftercollectively referred to as gaseous) saturated hydrocarbons into olefinsby heating while supplying oxygen. The hydrocarbons and, if desired,also the oxygen were id in some cases preheated before entry into thereaction chamber. If this heating of the gases be carried out separatelyand 'a temperature thereby attained at which the reaction between thehydrocarbons and the oxygen takes place without further external supplyof heat, there is then formed when working as hitherto usual. at theplace at which the hydrocarbons meet the oxygen, a flame or, when, asunder certain conditions is possible, this is avoided, at least a localoverheating. While this formation of flame or local production of heatis desirable in the known process for the conversion of saturatedhydrocarbons into acetylene, the conversion of hydrocarbons into olefinsis considerably impaired thereby. The yield of olefins diminishes andfurthermore the formation of oil and the separation of carbon takesplace.

We have now found that the said drawbacks while separately heating thehydrocarbons and an oxygen, or the former alone, which is carried outfor reasons of economy in heat, can be avoided if the oxygen when itmeets the preheated hydrocarbons is at once so much diluted that theformation of a'flame or local overheating does not take place while thetemperature of the mixture on account of the reaction smoothly rises toabove about 700 C. This dilution of the oxygen for the purpose ofavoiding its-local-enrichment in the gas mixture can be effected forexample by providing for the most rapid possible mixing of the oxygenwith the initial gas. This may be effected for example by introducingthe hydrocarbons, and if desired also the oxygen, into the reactionvessel with a high speed of flow. A rapid mixing may also be efiected bythe formation'of eddies at the place of mixing or by the tangen- I tialintroduction of one or both gases. The supply of the gases to the mixingplace may also be eflected through nozzles or porous walls, it being anessential however that a homogeneous mixing of the two gases takesplacein so short a time that strata or streaks of gas cannot be formed. Inexperiments with preheated industrial propane having a speed of flow of7 metres per sec- .5 0nd, when mixing it with similarly preheated oxygenthe formation of a flame took place at a mixing temperature of about 720C. only.

Another specially suitable means of producing a sudden strong dilutionof the oxygen is by mixing the hot gases under reduced pressure; it is Iimmaterial at what pressure the preheating has been carried out. Theadvantages of the mixing under reduced pressure may be further enhancedby the other means above described. Thus a preheated current of propanehaving a speed of from 17 to 18 metres per second and a pressure of 400millimetres (mercury gauge) at the place of mixing with a similarlypreheated oxygen gives no indication of any non-permissible localoverheating or even formation of flame at a temperature of 750 C. at theplace of mixing. The use of reduced pressure in the mixing processoffers the further practical advantage that the gases to be mixed can bebrought to high speeds in a very simple manner by the fall in pressure;,effective formation of eddies may be produced by deflecting bodies, insome cases even by ordinary filler bodies.

The dilution of the oxygen may also be effected by the supply ofvapours, as for example steam, or of gases, as for example carbondioxide, the formation of flame or local overheating thereby beingavoided. These vaporous or gaseous diluting media are hereinaftercollectively referred to as gaseous diluting media. 1

The conversion of the hydrocarbons into olefins is preferably carriedout in reaction vessels of non-metallic materials such as quartz, clayor chamotte. For the heating of the hydrocarbon gases, on the contrary,metallic apparatus is more suitable by reason of the better conductionof heat, as for example apparatus of iron-chromium alloys, and for thepreheating of the oxygen apparatus of alloy steels which are proofagainst oxidation. Any impairment of the yield of olefins ortroubles-such as deposition of carbon (such as may occur when carryingout the reaction in metal vessels or even when heating up mixtures ofhydrocarbons and oxygen), are not observed when the gases are heatedseparately in metal apparatus and the reaction is carried out innon-metallic vessels.

The following examples when taken with the accompanying self-explanatorydrawing, will serve to further illustrate the nature of this inventionbut the invention is not restricted to these examples. The drawingillustrates the apparatus employed in Examples 1 and 2, Figure 1 .beinga front elevation partly broken away of the apparatus of Example 1, andFigure 2 a cross section thereof, and Figure 3 an elevation partly insection of the apparatus oi Example 2.

Sample 1 30 litres of industrial propane preheated to 650' C. arecharged per hour under a pressure oi 400 millimetres (mercury gauge)through a quartz tube having a cross-section oi 40 square millimetres.Into this current of gas 10 litres per hour of cold oxygen areintroduced tangentially through a capillary tube having a cross-sectionof 2 square millimetres. The mixture attains a temperature oi. 880 C. inthe reaction chamber without external supply-oi heat, 80 litres ofoleflns being formed from each 100 litres of propane used and also CH4,Hz, CO. H20 and a littleCOz.

Example 2 40.7 litres of propane per hour and 14.5 litres of oxygen perhour are heated to 700" C. under a pressure of 400 millimetres (mercurygauge) in two separate tubes. the gases then being brought to a speed ofabout 20 metres per second at the place of mixing by capillaryrestriction of the tubes to a diameter of 2 millimetres. The mixturethen flows with a quiet reaction through a quartz tube widened to adiameter of 20 millimetres and charged with pieces of quartz, a maximumtemperature oi 870 C. being attained. The yield of oletlns amounts to'79 per cent of the volume oi the propane used.

Example 3 45 litres of ethane and 19.3 litres of oxygen per hour areseparatelypreheated to 700 C. in the apparatus described in Example 2and then mixed. In the attached reaction tube, which is widened to adiameter of 100 millimetres, a maximum temperature of 920 C. isattained. The

below about l000 0., the temperature at which substantial amounts ofacetylene are formed under the conditions obtaining while avoiding theformation of a flame or local overheating.

2. In the process as claimed in claim 1 the step of effecting the mostrapid possible mixing oi the oxygen with the initial gas.

3. In the process as claimed in claim 1 the step of effecting the mostrapid possible mixing of the oxygen with the initial gas by carrying outat least one of the steps consisting of introducing at least one of thesaid gases into the reaction vessel with a high speed of flow, causingthe formation oi eddies at the place of mixing, tangentially introducingat least one of the gases into the reaction vessel and introducing atleast one of the gases through nozzles at the place of mixing.

4. In the process as claimed in claim 1 the step of carrying out themost rapid possible mixing of the oxygen with the initial gas byintroducing at least one of the said gases into the reaction vessel witha speed of flow of more than about 5 metres per second.

5. In the process as claimed in claim 1 the step of maintaining thereacting gases under reduced pressure.

6; In the process as claimed in claim 1 the step of maintaining thereacting gases under reduced pressure and carrying out simultaneously atleast one oi. the steps consisting of introducing at least one of thesaid gases into the reaction vessel with a high speed of flow, causingthe formation of eddies at the place of mixing, tangentially introducingat least one of the gases and introducing at least one of the gasesthrough nozzles at the place of mixing.

7 In the process as claimed in claim 1, the step of producing a suddenstrong dilution of the oxygen by supplying a gaseous diluting medium.

8. In the process as claimed in claim 1, the step of producing a suddenstrong dilution of the oxygen by supplying steam.

9. In the process as claimed in claim 1, the step of producing a suddenstrong dilution of the oxygen by supplying carbon dioxide.

HANS KLEIN. FERDINAND HAU'BACH. WILHELM HOFEDITZ.

